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Sony Vfet Illustrated build guide
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Old 11th April 2020, 06:29 PM   #1051
Bones13 is offline Bones13  United States
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Sony Vfet Illustrated build guide
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Old 11th April 2020, 06:36 PM   #1052
Bones13 is offline Bones13  United States
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Old 17th May 2020, 08:22 AM   #1053
Jim50hertz is offline Jim50hertz  United Kingdom
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Daft question. I am replacing a nicely working Aleph J with this build from the DIYAudio kit. In terms of the PSU, which is the standard PSU with regulator boards intact, can I simply replace my toroid for the Aleph J with the (2x 22Vac secondaries) one for the VFet? Or do I need to replace R1-8 with different values?

PSU is the DIYAudio one.
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Old 17th May 2020, 08:46 AM   #1054
Rodeodave is offline Rodeodave  Austria
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Sony Vfet Illustrated build guide
Assuming your R1-R8 are 0R47 each, you'll be looking at something like 0R1 (four 0R47 in parallel) per polarity in your CRC PSU, which is perfect. See post #1 for reference.

You must however make absolutely sure that your PSU capacitors are rated for the higher supply voltage! That means caps rated for 35VDC or higher.
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Old 17th May 2020, 09:01 AM   #1055
Jim50hertz is offline Jim50hertz  United Kingdom
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Thanks Rodeodave! Yes, again this was a DIY audio kit, offered some years ago so 0R47. I'll double check the PSU capacitors voltage rating.
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Old 19th May 2020, 03:39 AM   #1056
Eric is offline Eric  United States
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Sony Vfet Illustrated build guide
Several years later and I finally found time to finish my VFet2 build. The boards have been stuffed for quite some time and I just picked up a chassis for it. It's a Dissipante 3U and sees a temp rise of about 23-24c.

The T-bar and heat sink needed a bit of work to mate better, so I used some valve lapping compound the scrubbed the two together for about 30-40 minutes to close the gaps. The transistors are mounted with ceramic oxide insulators and heat sink paste. I used a 400VA Antek transformer with TeaBag's CRC boards populated with 4 x 39kuF and 3 x 0R22 3w per rail.

After running for about 90 mins, I dialed in bias at 100mV and managed to reduce offset to about 10mV (at least for now). Those single-turn pots are a bit twitchy as others have pointed out, but with some patience it all works out.

Best of all - it makes music Only played with test speakers so far, need to finish up the chassis. Many thanks to Nelson for sharing such a great design and parting with so many vintage transistors and to 6L6 for the build guide!

Now I just need to find a place to put it. I think this is my 12th amp after hanging around here all of these years. My wife swears it's a sickness I still have bagged parts for another few amp projects...
Attached Images
File Type: jpg VFet2.JPG (658.1 KB, 126 views)
File Type: jpg Vfet measures.JPG (395.1 KB, 122 views)
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Old 19th May 2020, 03:45 AM   #1057
ggetzoff is offline ggetzoff  United States
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Quote:
Originally Posted by Eric View Post
Several years later and I finally found time to finish my VFet2 build. The boards have been stuffed for quite some time and I just picked up a chassis for it. It's a Dissipante 3U and sees a temp rise of about 23-24c.

The T-bar and heat sink needed a bit of work to mate better, so I used some valve lapping compound the scrubbed the two together for about 30-40 minutes to close the gaps. The transistors are mounted with ceramic oxide insulators and heat sink paste. I used a 400VA Antek transformer with TeaBag's CRC boards populated with 4 x 39kuF and 3 x 0R22 3w per rail.

After running for about 90 mins, I dialed in bias at 100mV and managed to reduce offset to about 10mV (at least for now). Those single-turn pots are a bit twitchy as others have pointed out, but with some patience it all works out.

Best of all - it makes music Only played with test speakers so far, need to finish up the chassis.

Now I just need to find a place to put it. I think this is my 12th amp after hanging around here all of these years. My wife swears it's a sickness I still have bagged parts for another few amp projects...

Eric,

Great job and thatís some stick-to-it-ness! We will look forward to your listening impressions.

Cheers,

Greg
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Old 19th May 2020, 09:52 AM   #1058
Berny is offline Berny  Belgium
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Quote:
Originally Posted by Eric View Post
The T-bar and heat sink needed a bit of work to mate better, so I used some valve lapping compound the scrubbed the two together for about 30-40 minutes to close the gaps.
I also found it was not mating very well... so I added some intermediate screws closer to the middle (one on top side that you can see and 2 on the bottom side) . I find the standard holes a bit too close to the border of the T-bar too. You can see on the picture the light shining between the T-bar and the sink when it was fixed without the additional screws (and without compound). Since the sinks are a bit on the small side, better not to loose too much heat conductivity on the way out ;-)

Very nice build! I like it when it is compact. I have the same case and put the transformer under the capacitors.
It is (currently) my best amp ever and use it daily
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File Type: jpg IMG-20200111-WA0001.jpg (325.2 KB, 118 views)
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Old 19th May 2020, 12:24 PM   #1059
Jim50hertz is offline Jim50hertz  United Kingdom
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Stuffed resistors. All good although on one of my boards I'm seeing 694r between T6-T11 and 722r between T8 -T13.

Any thoughts? T6 to T10 and T8-T12 testing slightly high too
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Old 19th May 2020, 12:43 PM   #1060
Dennis Hui is offline Dennis Hui  Canada
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Sony Vfet Illustrated build guide
I think the values are fine.

Also, which mosfets are you using for Q5 and Q6? If they are the
Fairchilds instead of the Toshibas you may need to increase the
resistances of R35/P3 and R34/P4 to bias the front end properly.
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